Ischemia-reperfusion is a pathological condition characterised by an initial restriction of blood flow to an organ followed by a subsequent restoration of perfusion and concomitant re-oxygenation. Perhaps surprisingly, restoration of the blood flow and re-oxygenation is frequently associated with an increase in tissue damage and a profound inflammatory response (“reperfusion injury”). Ischemia-reperfusion injury exists in a wide range of pathological conditions (Table 1).
TABLE 1Affected organExample of clinical manifestationIschemia-reperfusion of individual organsHeartAcute coronary syndromeKidneyAcute hypoxic renal injuryIntestineIntestinal ischemia-reperfusion; MODSBrainStrokeIschemia/reperfusion of multiple organsTrauma and resuscitationMODS; acute hypoxic renal injury;hypoxic intestinal injury; CTECirculatory arrestHypoxic cerebral injury; MODS; kidneydamageSickle cell anaemiaAcute thoracic syndrome; pulmonaryhypertension; acute hypoxic renal injurySleep apnoeaHypertension; diabetesIschemia-reperfusion in the course of surgeryCardiac surgeryAcute heart failure followingcardiopulmonary bypassThoracic surgeryAcute hypoxic pulmonary injuryPeripheral vascular surgeryCSEVascular surgeryAcute hypoxic renal injuryAcute transplant rejection; earlytransplant rejectionMODS (Multiple Organ Dysfunction Syndrome): Multiple organ dysfunction syndrome;CSE (Compartment Syndrome of the Extremity): Compartment syndrome of the extremitiesCTE (chronic traumatic encephalopathy): chronic traumatic encephalopathy caused by trauma from repeated blows (e.g., boxers, rugby players etc.)
The above-described ischemia-reperfusion-related pathological conditions derive from a set of biochemical events at cellular and tissue level. Once the blood flow has stopped in a given district, at a branch of the coronary artery for example, a series of biochemical processes takes place within the cells of the non-perfused tissues. While in the face of complete anoxia some of them undergo necrosis, the majority undergo a profound metabolic imbalance that is essentially characterised by a rapid increase of the intracellular content of reactive oxygen species (ROS, which include superoxide anion, O22−, hydrogen peroxide and the hydroxyl radical), by the low levels produced by the electron transport chain at amounts harmful to the cell. If the blood flow is restored (i.e. reperfusion), as occurs after angioplasty surgery, the amount of free radicals further increases, giving rise to extensive cell damage, which configures the “ischemia-reperfusion” condition. This situation, which is essentially a massive redox shock, is not only directly harmful to various macromolecules within the cell (proteins, nucleic acids, lipids), but is capable of triggering the intrinsic pathway of apoptosis.
Indeed, in myocardial infarction, up to 80% of the extension of the final lesion is linked to apoptotic death, which completes in hours to days following the onset of the ischemia-reperfusion condition.
From a biochemical viewpoint, the intense metabolic shock activates a large number of molecules that act as redox sensors, such as ASK-1 kinase. This kinase is maintained in an inactive state by the bond with reduced thioredoxin and glutaredoxin; the oxidation thereof determines their detachment from ASK-1 and the consequent functional activation of the kinase.
Other pathways involved from the outset of the process include AMP kinase and Rho GTPase. Operating in synergy, these systems can reciprocally influence each other, thus significantly amplifying the apoptotic process. A functionally coherent family of kinases located downstream of the above-described metabolic pathways, consists of the JNK and p38 MAPK (MAP-kinase) proteins, which represent a common node of the chain of signal transmission chain. These molecules have cytosolic and nuclear substrates, that are in part shared, which participate in various ways to the processes of cell death by autophagy or apoptosis. To cite a few examples, JNK and p38 MAPK bind and phosphorylate Bcl-xL and Bcl-2, inactivating the anti-apoptotic potential thereof, an event followed by the release of cytochrome c from the mitochondrion, the combination thereof with molecule Apaf-1 and the consequent activation of caspase-9. Other critical targets of the two MAP-kinases are Beclin-1 and p53, both closely related to the onset of autophagic and apoptotic cell death, respectively.
On the basis of the above-reported considerations, it can be stated that the MAP-kinase are critical for the generation of the cell damage that takes place in a number of clinical contexts, in particular in conditions of ischemia-reperfusion. It is also interesting to note that p38 MAPK and JNK share a common biochemical modulator, MKP-1, a phosphatase specifically capable of inactivating the MAP-kinase enzyme family.
A number of studies have directly demonstrated this statement; for example, knock-out mice for p38 MAPK, following the closure of branches of the coronary artery, have greatly reduced myocardial lesions with respect to the normal controls, a finding that emphasises the role of these kinases in the generation of tissue damage.
It is thus in the state of the art that for the treatment of ischemia-reperfusion-related pathologies or for the use in medical procedures involving ischemia-reperfusion, a useful pharmacological approach can be achieved through the use of compounds that are capable of modifying the activity of the MAP kinases family. Patent WO2004000324 sets out that 3-azabicyclo[3.2.1]octan derivatives are active as agonists of human neurotrophins and are therefore useful for the preparation of pharmaceutical compositions for the treatment of diseases in which the neurotrophin functions, particularly NGF functions, are implicated by default:
neurodegenerative disorders of the central nervous system, such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Huntington's disease, neuropathies, neural damage caused by hypoxia, ischemia, or trauma, inducing apoptosis of the nerve cells;acquired immunodeficiency diseases linked to reduced bioavailability of NGF, such as age-related immunodeficiency;diseases in which neoangiogenesis stimulation proves advantageous, such as myocardial infarction, stroke, or peripheral vascular diseases;certain diseases of the eye, such as keratitis of diverse aetiology, glaucoma, degenerative or inflammatory conditions of the retina.has been described as intermediate for the synthesis of a spiro-beta-lactam in A. Trabocchi, et al. Eur. J. Org. Chem. 2007, 4594-4599.
The (1R,5S,7R)-3-(p-methoxybenzyl)-2-oxo-6,8-dioxa-3-azabicyclo[3.2.1]octan-7-carboxylic Acid compound has been described as peptidomimetic in Antonio Guarna, et al J. Org. Chem. 1999, 64, 7347-7364.
The (1R,5S,7R)-3-Benzyl-2-oxo-6,8-dioxa-3-azabicyclo[3.2.1]octan-7-carboxylic Acid compound and the (1R,5S,7R)-3-(p-phenyl)-benzyl-2-oxo-6,8-dioxa-3-azabicyclo[3.2.1]octan-7-carboxylic Acid compound were described as inhibitors of metalloproteases in C. Mannino et al. Bioorganic & Medicinal Chemistry 14 (2006) 7392-7403.
The synthesis of the (1S,5R,7S)-3-ethyl-2-oxo-6,8-dioxa-3-azabicyclo[3.2.1]octan-7-carboxylic acid compound is described in Reymond, J-L.; et al. Tetrahedron Asymmetry 1990, 1(10), 729-736.
The object of the present invention is to provide compounds for the treatment of ischemia-reperfusion-related pathologies or for use in medical procedures involving ischemia-reperfusion, and in particular, but not exclusively, those characterised by an inappropriate variation in the activities of the MAP kinases family.